1. Field of the Invention
The present invention relates to a cylindrical lock with improved resistance to torque.
2. Description of the Related Art
FIGS. 1 and 2 of the drawings illustrate a conventional cylindrical lock with lever handles for people that are handicapped in hands or rely on wheelchairs. The cylindrical lock includes a lock main body 1 mounted in a mounting hole 91 of a door 9. The lock main body 1 includes a substantially cylindrical hub 11 comprised of an inside hub 111 and an outside hub 112. A transmission assembly 12 is mounted in the hub 11 and includes an inside spindle 121, an outside spindle 122, and a retractor 120. The inside hub 111 includes a sleeve portion 113 with two diametrically opposed chamfered faces 114. The outside hub 112 includes a sleeve portion 115 with an outer threading. An inside rose liner 13 is mounted around the sleeve portion 113 of the inside hub 111 and has a central hole 131 with two diametrically opposed rectilinear sections 132 for engaging with the chamfered faces 114 of the inside hub 111. An outside rose liner 14 is mounted around the sleeve portion 115 of the outside hub 112 and has an inner threading 141 for threadedly engaging with the outer threading of the sleeve portion 115 of the outside hub 112.
The cylindrical lock further includes a latch mechanism 2 attached to the lock main body 11, an inside rose 32, an outside rose 42, a lever type inside handle 31, and a lever type outside handle 41. The latch mechanism 2 includes a latch 21 operably connected to the retractor 120 mounted in the lock main body 1. The latch 21 is retracted when the retractor 120 is actuated. The inside rose 32 covers the inside rose liner 13 and abuts against an inner side of the door 9. The outside rose 42 covers the outside rose liner 14 and abuts against an outer side of the door 9. The inside handle 31 has an end connected to the outside spindle 121 to turn therewith. The outside handle 41 has an end connected to the outside spindle 122 to turn therewith. Turning of either handle 31, 41 causes movement of the retractor 120, which, in turn, retracts the latch 21 to thereby allow opening of the door 9.
In the above cylindrical lock, the inside rose liner 13 and the outside rose liner 14 are important elements for positioning. Two diametrically opposed mounting rods 15 project from a side of the outside rose liner 14 and each includes a screw hole 151 in a distal end thereof. The inside rose liner 13 includes two diametrically opposed holes 130. Two bolts 16 are respectively extended through the holes 130 of the inside rose liner 13, two positioning holes 92 in the door 9, and the screw holes 151 of the mounting rods 15 on the outside rose liner 14, thereby securing the lock main body 1 to the door 9.
The outside rose liner 14 can be turned and thus move along an axial direction via threading engagement between the outer threading of the sleeve portion 115 of the outside hub 112 and the inner threading 141 of the outside rose liner 14 until the lock main body 1 reaches a desired position corresponding to the thickness of the door 9. Thus, the retractor 120 is aligned with a tail portion of the latch 21.
The above cylindrical lock is simple in its positioning structure and thus can be manufactured at a low cost. However, the torque generated as a result of pressing the inside handle 31 of lever type or the outside handle 41 of lever type is considerably greater than that generated on a knob type handle, and it was found that the inside rose liner 13 and the sleeve portion 113 of the inside hub 111 could not resist excessive torque resulting from excessive force applied to the lever type handle. As a result, the elements of the cylindrical lock are apt to be damaged.